Protecting-shell for spark-plugs



l. R. HICKS. PROTECTING SHELL FOR SPARK PLUGS.

APPLIQATXON H LED DEC. 5, 1918- I Patented Aug. 23, 1921.

. partly broken away to illustrate the con- UNITED STATES IRL R. HICKS, 0F CENTRALIA, MISSOURI.

j rnoTEoTTNG-SHELL Fon SPARK-PLUGS.'

`Specification of Letters Patent.

Patented Aug. 23, 1921.

Application led December 5, 1918. Serial No. 265,422.

`SparlrPlugs, of which the following is a specification.

j T his invention comprehends generally imn proveniente in that class of inventions known as spark plugs and more particularly relates to a protecting shell for spark plugs.

lt is a well known fact that when an engineis hot and the outside portion of the porcelain core ofthe spark plugs in the engine is, exposed to a sudden cold draft of air, rain or snow, that the porcelain core will crack near its point of connection with the sparkplug base and be rendered useless. It is'the principal aim and object of this invention therefore to provide a pro; tecting shell formed of insulating material and designed to be arranged about the plug and spaced from the porcelain core thereof to provide an air chamber about the core and thereby shield the core from sudden changes of temperature and in consequence prevent the breakage of the core.

It is a more specilic object of this invention to provide a device of the above mentioned character wherein the body of the shell is of novel construction; and to also provide a reinforcing eyelet about the opening in the top of the shell.

Among the other aimsand objects of this invention may be recited the provision of a device of the above mentioned character wherein the number of parts are comparatively few, the construction'simple, the cost of Jroduction low and the eficiency high.

ther objects, as well as the nature, characteristic features and scope of this invention will be more readily apparent from the following description taken in .connection with the accompanying drawings and pointed out in the claims, forming a part of this specification.

In the accompanying drawings, the figure represents a side elevation showing the shell applied to a spark plug', the `shell being struction thereof. n

Referring now, more particularly, to the accompanying drawings, there is illustrated` a spark plug indicated in its entirety by the numeral 1 desirably of the usual form although it may be stated to consist generally of a main central electrode 2 about which is arranged a porcelain core 3 the lower end of which is mounted in the hexagon shaped attaching base 4 in the usual manner and the upper projecting threaded portion of the central` electrode has detachably mounted thereon thev terminal clamping nut 5 which acts as a means for releasably holding the improved protecting shell generally designated 6 in the p-roper position on the spark plug.

In reducing the present and improved construction of shell to practice, the saine may be said to consist of a cap-like body 7 formed of insulating material the main portion of which is desirably of a hexagon` configuration in cross section so as to lit snugly about the upper portions of the sides of the correspondingly spaced base et of the spark plug while the upper portion of the body of the shell is restricted to provide a top 8 which is preferably rounded and formed with a central opening 9 for disposition about the upper projecting portion of the electrode, before the application of the clamping nut 5, and on the upper end of the porcelain core 3. lVhen in this position, an Aair space or chamber 10 is provided between theouter surface of the core 3 and the inner surface of the shell to protect the porcelain core from sudden changes of temperature and thereby prevent breaking of the core.

It is preferred that a metallic eyelet l1 be fitted in the opening 9 for reinforcing and protecting the top 8 about the opening therein, and, subsequent to the application of the shell the clamping nut 5 is engaged with the threaded projecting portion of the central electrode 2 for clamping the shell in the proper position, the clamping action being on the eyelet ll instead of on the top of the projecting shell, thereby increasing the longevity of the device, as is apparent. It is also preferred that the lower outer edge of the body of the shell be rounded as at l2 thereby relieving the projecting corners as is apparent. l

It is evident that the shell may be applied to substantially any standard type of spark plug without any modification whatever in the original construction thereof, and when so applied will effectively protect ap ended claims.

trode of said plug when .the insulator of the lug against'the danger ofrapid cooling an venting the insulator broken.

Still further embodiments ofthe invention than those herein especially defined may be resorted to as conditions or preference ma dictate, as may be 4in keeping with the hereto rovide a guard prerom being struck and aving thus fully described the invention,

what is claimed as new and desired to besecured by Letters Patent, is: 1. A protectin shell for spark plugs comprising a cylin rical body having a convexed closed end and an -opposite open end,l

said closed end having a central aperture therein adaI ted to receive the central electhe body is telescoped thereover, said body being freelyremovable therefrom, and being of a diameter considerably greater thanvthe upper rtion of the lug to space the inner sur ace of said .body from the shell of the plug and having its open end shaped correspondingly to the shell of said plug to snugly embrace the same.A

2. A rotecting shell for spark lugs construct of insulating material and) comprising a cylindrical body having a convexed closed and an opposite end, said closed end having a central aperture therein for receiving avreinforc' eyelet to space the to of the body frommie shell of the spark pllu and adapted to receive the central elect e of said plug when the body is telesco thereover, said eyelet also constituting a bearing surface for the terminal clampln nut of said lug, said body being of a d1- ameter considerably greater than the upper rtion of the plug to space the inner surace thereof from the body of the shell and having its open end shaped correspondingly to the circumference of embracing the same sion of dirt or oil.

In testimony whereof I aflix my signature hereto.

IRL R. HICKS.

the shelland snugly to prevent the admispedas 

